Felipe Massa believes Williams will be able to give Mercedes a good run for their money at Spa and Monza.
The Grove squad have enjoyed an excellent first half of the season, picking up 135 points with three podiums to lie fourth in the Constructors' Championship.
The team, though, didn't have the best of outings - by their lofty standards this season - at Hungary last time out as the track didn't really suit the team and Massa finished fifth and his team-mate Valtteri Bottas down in eighth.
Teams are now on a three-week break, but once the season resumes Massa is confident they are in for an excellent second half to the 2014 campaign.
"I'm sure we can have a very good second half of the season looking at the behaviour of the car until now," the Brazilian said.
"Spa and Monza should suit us, maybe Austin and Brazil, and in the last race in Abu Dhabi there are some good straights.
"The car can be competitive at many tracks, not just Spa and Monza, but maybe at those two we can be stronger than the others. It won't be easy, but it's not impossible that at these tracks we will have more of a chance against Mercedes."
After a tough 2013 campaign during which they scored only five points, Williams have taken major strides forward this season with the FW36, much to Massa's delight.
"Everybody has been surprised at the competitiveness of the car," added Massa.
"I obviously expected to have a much better car than the team had in the past, this was clear, but it was too much to think about doing so well in the Championship.
"What we have done from the winter through to now has been a very good job from everybody on the technical side.
"There is still a lot we can do, but everything is progressing in a good way in terms of development, and I hope we can do even more from now until the end of the season."